From 0b2fa3282f96a82108b45f98b3e78d26a3baaa80 Mon Sep 17 00:00:00 2001
From: Yaakov <git@yaakov.dev>
Date: Sun, 11 Aug 2024 14:42:56 +1000
Subject: [PATCH] works now, clean me up pls

---
 scream.c | 95 ++++++++++++++++++++++++++------------------------------
 1 file changed, 44 insertions(+), 51 deletions(-)

diff --git a/scream.c b/scream.c
index c52d630..5401051 100644
--- a/scream.c
+++ b/scream.c
@@ -3,6 +3,7 @@
 #include <linux/fs.h>
 #include <linux/cdev.h>
 #include <linux/device.h>
+#include <linux/kernel.h>
 #include <linux/uaccess.h>
 
 MODULE_AUTHOR("Yaakov");
@@ -20,87 +21,79 @@ static struct cdev scream_cdev;
 static int scream_device_open(struct inode*, struct file*);
 static int scream_device_release(struct inode*, struct file*);
 static ssize_t scream_device_read(struct file*, char*, size_t, loff_t*);
-static ssize_t scream_device_write(struct file*, const char*, size_t, loff_t*);
 
-static struct file_operations fops = {
+static const struct file_operations scream_fops = {
+    .owner      = THIS_MODULE,
     .open = scream_device_open,
     .read = scream_device_read,
-    .write = scream_device_write,
     .release = scream_device_release,
 };
 
-static int __init scream_module_init(void) {
-    printk(KERN_INFO "[scream] loading...\n");
+static int __init scream_module_init(void)
+{
+    int err;
+    dev_t dev;
 
-    if (alloc_chrdev_region(&major_number, 0, 1, DEVICE_NAME) < 0) {
-        printk(KERN_ALERT "[scream] Failed to register a major number.\n");
-        return major_number;
-    }
+    err = alloc_chrdev_region(&dev, 0, 1, DEVICE_NAME);
+
+    major_number = MAJOR(dev);
 
     scream_class = class_create(CLASS_NAME);
-    if (IS_ERR(scream_class)) {
-        unregister_chrdev_region(major_number, 1);
-        printk(KERN_ALERT "[scream] Failed to register device class\n");
-        return PTR_ERR(scream_class);
-    }
-    
-    scream_device = device_create(scream_class, NULL, MKDEV(major_number, 0), NULL, DEVICE_NAME);
-    if (IS_ERR(scream_device)) {
-        class_destroy(scream_class);
-        unregister_chrdev_region(major_number, 1);
-        printk(KERN_ALERT "[scream] Failed to create the device\n");
-        return PTR_ERR(scream_device);
-    }
 
-    printk(KERN_INFO "[scream] %s/%s device registered.", CLASS_NAME, DEVICE_NAME);
+    cdev_init(&scream_cdev, &scream_fops);
+    scream_cdev.owner = THIS_MODULE;
 
-    cdev_init(&scream_cdev, &fops);
-    int add_result = cdev_add(&scream_cdev, MKDEV(major_number, 0), 1);
-    if (add_result < 0) {
-        device_destroy(scream_class, MKDEV(major_number, 0));
-        class_destroy(scream_class);
-        unregister_chrdev_region(major_number, 1);
-        printk(KERN_ALERT "[scream] Failed to add cdev: %d\n", add_result);
-        return -1;
-    }
+    cdev_add(&scream_cdev, MKDEV(major_number, 0), 1);
+
+    device_create(scream_class, NULL, MKDEV(major_number, 0), NULL, DEVICE_NAME);
 
-    printk(KERN_INFO "[scream] loaded.\n");
     return 0;
 }
 
-static void __exit scream_module_exit(void) {
-    printk(KERN_INFO "[scream] exiting...\n");
-
-    cdev_del(&scream_cdev);
+static void __exit scream_module_exit(void)
+{
     device_destroy(scream_class, MKDEV(major_number, 0));
+
+    class_unregister(scream_class);
     class_destroy(scream_class);
-    unregister_chrdev_region(major_number, 1);
 
-    printk(KERN_INFO "[scream] done.\n");
+    unregister_chrdev_region(MKDEV(major_number, 0), MINORMASK);
 }
 
-static int scream_device_open(struct inode* node, struct file* file)
+static int scream_device_open(struct inode *inode, struct file *file)
 {
-    printk(KERN_INFO "[scream] opening device.\n");
+    printk(KERN_INFO "[scream] Device open\n");
     return 0;
 }
 
-static int scream_device_release(struct inode* node, struct file* file)
+static int scream_device_release(struct inode *inode, struct file *file)
 {
-    printk(KERN_INFO "[scream] releasing device.\n");
+    printk(KERN_INFO "[scream] Device close\n");
     return 0;
 }
 
-static ssize_t scream_device_read(struct file* file, char* __user user_buffer, size_t size, loff_t* offset)
+static ssize_t scream_device_read(struct file *file, char __user *buf, size_t count, loff_t *offset)
 {
-    printk(KERN_INFO "[scream] reading from device.\n");
-    return 0;
-}
+    uint8_t rand;
 
-static ssize_t scream_device_write(struct file* file, const char* __user user_buffer, size_t size, loff_t* offset)
-{
-    printk(KERN_INFO "[scream] writing to device.\n");
-    return 0;
+    for (size_t i = 0; i < count; i++)
+    {
+        get_random_bytes(&rand, sizeof(rand));
+
+        char value;
+
+        if (rand > 200) {
+            value = 'A';
+        } else {
+            value = 'a';
+        }
+
+        if (copy_to_user(buf + i, &value, 1)) {
+            return -EFAULT;
+        }
+    }
+
+    return count;
 }
 
 module_init(scream_module_init);